Viroids, Obelisks, and Viruses Explained

By Peter A. McCullough, MD, MPH

The COVID-19 pandemic has forced citizens to become closet virologists and immunologists straining to understand the dizzying array of medical and laboratory jargon. Recently the public was hit with a few new terms: viroids and obelisks.

Viroids are infectious agents that consist only of naked RNA without any protective layer such as a protein coat. Viroids infect plants (but no other forms of life) and are replicated at the expense of the host cell. Viroid genomes are small single-stranded circles of RNA that are only 250–400 bases long.

Obelisks are microscopic entities, which were recently discovered by a team led by Dr. Andrew Fire at Stanford University using computational analyses from large posted samples of genetic code. They are circular bits of genetic material that contain one or two genes and self-organize or fold into a hair-pin curve yielding a rod-like shape. Obelisks include circular RNA genome assemblies with around 1000 base pairs, the rod-like secondary structures encompass the entire genome. In contrast to viroids, their RNA is translated into proteins, tentatively called "oblins".

doi: 10.1126/science.znxt3dk